In the heddle frames of a heddle frame weaving machine, the heddles have eyelets at both ends thereof and each end is threaded onto upper and lower heddle frames or on thread rails which are provided thereat. This type of connection is provided so that the heddles can move in transverse direction with respect to the direction of movement of the heddle frame, however, in the heddle frame plane. It is known to dimension the end eyelet in such a manner that the connection to the thread rails has an all-round clearance, a so-called free floating characteristic.
This free floating characteristic permits the heddles to align themselves in the heddle frame corresponding with the position of the warp threads which they guide. One speaks of a self-alignment characteristic. This free movability between the heddle and the thread rail may lead to a premature wear in particular of the eyelet ends on the heddles. This wear is increased, if due to the movement of the heddle frame unidirected vibrations are present.
The free movability of the heddles has still further disadvantages. In fast-running weaving machines, the heddle frames are accelerated and stopped at forces exceeding lg. In both instances, one eyelet end of the heddle is released a short distance from its endmost position with respect to the thread rail on which it is threaded. The peripheral edge of the other end eyelet engages its associated thread rail. These constant jerking and engaging movements result in worn eyelet ends, tears in the heddle material and gashes or cuts in the thread rails. Furthermore this action creates much noise.
The goal of the present invention is to provide a quieter movement of the heddle frames for the purpose of increasing the production speed, avoiding standstill times which have been caused by damaged material and effect a reduction of the operating noise of the weaving machine.
This goal is achieved with one of the abovementioned weaving machines, which is inventively characterized by means being arranged to periodically change the distance between the two thread rails of one heddle frame.
The free floating feature can therewith be cancelled periodically. A constant cancellation of the free floating feature would result in the disadvantage that the heddles could no longer adjust to the position of the warp threads.